This is a U.S. original patent application which claims priority on Great Britain patent application No. 0113857.7 filed Jun. 7, 2001.
This invention relates to the field of photographic film and paper processing machines, in particular to the chemical delivery systems for the machines.
In existing photographic processing machines the chemicals have to be replenished in order to keep their chemical activity constant. If this is not done the photographic result will vary unacceptably due to the active chemicals being consumed by rendering the image visible and also by the action of oxidization over time with the oxygen in the atmosphere.
In some machines replenishment is achieved by using metering pumps which are accurately set to deliver cold replenisher solution directly into the hot working tank. The temperature effects are minimized by the large volume of solution in the process tank. The replenisher also raises the level in the tank and the surplus normally runs to waste over a weir arrangement. Depending on point of replenisher delivery it is possible to lose some fresh as well as used solution. When this arrangement is used the fresh chemicals are normally drawn directly by the metering pumps from tanks or delivery cans close to the point of use.
In larger machines it is normal to hold the replenisher in tanks (several 1000 liters) some distance from the point of use. In this instance gravity is frequently used to drive the solution down to set measuring glasses. The solution is admitted to the glass by an electrically operated valve on an instruction from the machine control system. An electrical level probe is set in the glass to switch off the solution supply when the pre-set amount is reached. A lower valve is then opened allowing the solution to flow down into the process machine tank. Volumetric measuring glasses are used in the Hostert leaderbelt machine. It is also known for accurate turbine flow meters and vortex shedding devices to be used in place of metering pumps and volumetric measuring glasses.
For example, a turbine flow meter is used in the San Marco TM xe2x80x9cFlexileaderxe2x80x9d machine.
All of these delivery systems consisting of replenisher solution tanks, working process tanks and waste tanks are designed to keep chemistry at constant activity levels over long periods. It also assumes the machine is used four or five times a day with a range of average subjects. As the subjects vary and the fresh chemistry is added in fixed predetermined volumes long-term activity drifts occur. To prevent this process check exposures are normally passed through the process and depending on the results the tank is either spiked with extra replenisher or diluted.
The above methods are unsuitable for small machines used intermittently without supervision or for machines where the chemistry is used once and then discarded.
This invention aims to overcome all of the above limitations particularly when applied to walk up machines which do not have process tanks holding solutions, which are used intermittently without supervision and where just sufficient volumes of fresh chemistry is dispensed, on demand, for one process cycle.
This invention is a system for holding and delivering at working temperature volumes of liquids into any type of photographic or other processor quickly by the use of a xe2x80x9cdumpxe2x80x9d valve. It is specially designed to minimize wetting effects and improve uniformity in single use chemical process cycles or processes with short process cycles of less than 25 seconds. The invention can also be used in combined single use and short time process cycles.
According to the present invention there is provided a delivery system for a processor comprising means for supplying solution to an airtight chamber, heating means for heating the solution within the chamber, means for transferring a predetermined volume of heated solution from the airtight chamber to a holding chamber and means for releasing the heated solution from the holding chamber such that the solution drops into the processor. Preferably the airtight chamber has a plurality of solution chambers which may hold different solutions. The solution chambers may also vary in volume if desired.
The invention further provides a method of supplying processing solution to a processor comprising the steps of supplying solution to an airtight chamber, heating the solution within the airtight chamber, transferring a predetermined volume of heated solution from the airtight chamber to a holding chamber and dropping the heated solution from the holding chamber into the processor.
The invention provides numerous advantages.
It is easy to change the volumes of solution by changing the number of complete cycles made by the pump. Due to the sealed system the chemistry is kept at the required temperature which substantially eliminates oxidation. The chemicals are also delivered at the correct temperature. There is no warm up or waiting time. The chemicals are delivered quickly which improves uniformity in single use systems. There is less heat loss from the small airtight chambers.
All solutions are handled by one valve which is self cleaning. Solution drain back is prevented by using simple non-return valves in the valve assembly. This ensures accurate delivery from the first pump stroke. The holding cartridge is able to accommodate all of the different volumes used in the process. The holding cartridge can be designed with a plurality of solution chambers. The solutions can be a different temperature to the process vessel enabling the process to be either xe2x80x9ckick startedxe2x80x9d or xe2x80x9csoft startedxe2x80x9d according to the particular process requirements.